1. Field of the Invention
The present invention relates to a mobile communication apparatus, and more particularly, to a mobile communication apparatus capable of performing group communication between a cellular communication system and a VoIP system.
2. Description of the Prior Art
Mobile communication has become a boom industry during recent years. Many kinds of wireless communication technologies have been developed. Taking mobile phone systems for example, there are several kinds of widely applied mobile phone systems, which are the GSM system (which stands for Global System for Mobile Communications), the CDMA system (which stands for Code Division Multiple Access system), and the WCDMA system (which stands for Wideband Code Division Multiple Access system), etc.
The reduction in cost of the mobile phones has placed them in the affordable range of most people. Due to the rapid progress in technology, more functional and powerful mobile phones are constantly being invented. In order to meet customers' demands, the mobile phone manufacturers often add many new functions and techniques to the mobile phone. For example, a digital camera function and an external keyboard interface are embedded in most of the latest mobile phone, both increasing convenience and enhancing the users' lifestyle.
In other aspects, due to the popularity of personal computers (PCs) and the Internet, a VoIP system (which stands for Voice over Internet Protocol system) has been developed. The VoIP system provides an alternate selection for users to communicate with each other instead of utilizing a traditional phone. Generally, the VoIP system utilizes a specific program run on the PC for exchanging audio packets to provide high-quality voice communications through the Internet. Furthermore, due to the wider band of the Internet, the VoIP system not only provides real-time voice communications, but also provides additional services such as image transmitting and file exchanging. Therefore, users are not limited to utilizing a traditional telecommunications (telecom) system. In addition, the VoIP system saves users money because users pay a low price charged by the Internet service provider rather than the comparably higher price charged by the telecom system provider.
In order to combine the advantages of both the cellular communication system and the VoIP system, a dual-mode mobile communication apparatus such as a personal digital assistant phone (Wi-Fi phone) has been developed. However, the telecom system provider for the cellular communication system and the Internet service provider for the VoIP system are different, and the communication techniques are also different. Therefore, if there is no cross-link service provided by the cellular communication system and the VoIP system, the cross-network group communication among the dual-mode mobile communication apparatus, the cellular communication system, and the VoIP system cannot be achieved, which places inconvenient limitations on the users.